Heat Sticks "on"

[DSM Turbos]

2000 1500 Z71

 

Whenever I turn on the heat on my truck, it will never want to go back down to being cool until I turn off the truck. Basically if I turn the heat on or even the dial all the way to hot, then try to move it to cool, even with it 45 degrees outside and the ac on the temps will not cool down at all that the truck is blowing out. Any ideas on what might be causing that? Stuck switch of some sort?

[jchilling]

I posted the same question about 2 nights ago. I have the exact same problem in my 2001 Tahoe. It seems that the "blend damper actuator" may be bad. I went out and bought a new one from GM parts direct and installed it. My problem is still there. I can turn up to about 75% and then go back to cool but if I go beyond 75% on up to 100% it stays hot. If I park the truck for an hour or so it returns to cool again.

 

What I've found out:

 

This often happens over time if you disconnect the battery for some reason.

 

The damper door travel limits apparently wear over time and when you reconnect the battery, the actuator and its associated microprocessor control run a limit test cycle which exceeds the values pre-programmed to the module. Result: it no longer "knows" where it is positioned. I'm seeing documents now (from a corvette site) about "reindexing" the actuator by pulling it, opening the device and rotating gears a couple of teeth to return the travel back to within limits. Attached are some links concerning this:

 

http://www.gm-trucks.com/forums/index.php?showtopic=69682

 

http://vette.the-reeds.com/actuator/actuator.htm

 

the last link was at www.fullsizechevy.com/forums under the "technical bulletins" forum there's a complete instruction for replacement of the actuator along with my question about what to do next. I'm still hangin' on this site and FSC.

 

That's about all I know for right now. Best of luck, let me know if you find out more and I'll post again if I solve this one.

[DSM Turbos]

Yeah, seems very close to your problems. FSC seems to be down for me tonight?

 

I wonder how much a dealer would charge to fix it.

 

A guy on a local board posted

 

"been selling alot of heat /ac controllers a work on the main board hot / cold will heat up and bleed together once it cools down or gets turn off it will work fine for short time pull the controller out should be two clips or two 7mm bolt look at board for hot spot other thing would be the box behind the dash but it will still switch from def to vent ,floor ?"

 

But his post is more confusing them helpful to me. I am guessing he means the actuator like you? How much is that part? It seems like it maybe a combination of both?

[jchilling]

I don't know what the stealers will charge. Sounds like the quote is describing the control board behind the dash - not the actuator - maybe, you're right, that's a very confusing post. There are two actuators, the one that controls heat/cool is fairly easy to get to, the other actuator is up behind the dash and controls air flow (floor, vent, defrost, mix, etc). The actuator was $38 + freight. Dealer price was around $52 or so.

[DSM Turbos]

Got a part number for the actuator that you got?

 

found a guy with an 01 suburban that said this fixed it

 

If your temperature control stays hot even when you turn it all the way to cold, the culprit most likely is the temperature control actuator. This thread tells you how to change it.

Tools required:

1/4" drive ratchet

7 mm socket

5.5 mm socket or 7/32" will work

1 1/2" extension

Parts

GM # 52474810 Actuator Have the dealer double check this. I know this is the correct number for 99 to 02.

 

Step one

Using the 7mm socket remove the 3 screws holding the passenger side underdash trim panel. The screw above the transmission hump is a pain so be careful and take your time removing it.

 

Step two

Once the panel is out of the way, the actuator is toward the center of the truck. The electrical plug comes in from the bottom and has 5 wires, unplug it. There are 2 screws holding the actuator in, one on the left and one on the right. Using the 5.5 mm or 7/32" socket, remove the screws. Once the screws are removed, the actuator will come off straight down.

 

Step three

Once the old unit is off, you'll notice the shaft that the actuator slides on has 2 flats on it. Looking at the new actuator, turn the shaft until it's lined up. Slide the new actuator up onto the shaft, line up the screws and reinstall them. Plug the actuator back in.

 

Step four (Very important)

Turn the temp control all the way to cold. Pull the HVAC 1 fuse (panel on the drivers side of the dash, top front fuse). Turn the ignition key to run. Leave the key on for at least 1 minute. Turn the key off and put the fuse back in.

 

Step five

While you have the trim panel off it's a good time to check your cabin air filters (if you have them). About halfway between the transmission hump and the door there is a plate that is about an inch wide, you’ll see a single screw (toward the firewall) holding the cover plate in place. You’ll need a 5.5 mm socket to remove this screw. After the small cover plate is removed, you’ll see one of the filters in the housing. Pull the filter down and out of the housing. You may need to rotate the filter as you pull it down. After the first filter is removed, look inside the housing, and you’ll see the second filter. Just slide it out, pull it down and out of the housing just like the first one.

When reinstalling the new filters, make sure you have the arrow (airflow) on them pointing in the right direction, towards the driver’s side of the truck.

 

Step six

Reinstall the cover panels and you are done.

[jchilling]

Sorry I was out of town - travel for a living. Yeah, that's exactly where I got my info - FSC. THat's the right part number and that's what I did but I ended up with the problem I have now - anything past 75% heat and it won't return to cool.

[wgabert]

I had the same problem a year ago. Before you go and spend your hard earned money on a new temp actuator give this a try. On some units it appears that the actuator is pushing up on the door causing it to bind. I removed the actuator and installed a couple of small washers between the mount and the actuator at the screw mounts. Problem was solved and has never returned

 

warren

[jchilling]

Interesting, I'll give that a shot in the next day or two.